Miniature electrochemical cell having a casing comprising opposed ceramic substrates secured together using a precious metal braze

ABSTRACT

A miniature electrochemical cell having a volume of less than 0.5 cc is described. The cell has a casing of first and second ceramic substrates that are hermetically secured to each other to provide an internal space housing an electrode assembly. First and second conductive pathways extend through the ceramic substrates. The pathways have respective inner surfaces that are conductively connected to the respective anode and cathode current collectors and respective outer surfaces that provide for connection to a load. An electrolyte in the internal space of the housing activates the electrode assembly.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. provisional patentapplication Ser. No. 62/517,408, filed on Jun. 9, 2017.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to the art of electrochemical cells. Moreparticularly, the present invention relates to an improved miniatureelectrochemical cell, which is defined as a cell having a total volumethat is less than 0.5 cc.

2. Prior Art

Conventional miniature electrochemical cells are primarily designed ascoin cells, which is a convenient configuration for the assembly ofsmall cells. A typical coin cell has a metal base and a metal lid thatserve as the opposite polarity terminals for the cell and areelectrically isolated from each other by a plastic gasket. A seal isformed by crimping the metal base around the gasket. The plastic gasketthen electrically isolates the base and lid from each other. However,seals formed by crimping a metallic member onto a plastic gasket aredifficult to form consistently and are known to be unacceptably porousfor hermetic applications. A compromised hermetic seal may present anescape path for electrolyte or allow for atmospheric contaminants to getinside the cell and disrupt its operation. Ingress of water isparticularly problematic for lithium electrochemical cells. In thatrespect, crimped plastic seals may not provide the type of consistentlongevity from one cell to the next that is required for someapplications, particularly when the cell is intended to power a deviceimplanted in a human or animal body.

In addition, the crimped metal/plastic seal has a certain peripheralvolume requirement that reduces space for the electrodes, therebyreducing cell capacity and energy density. A conventional coin cell witha crimped seal may not have sufficient energy per unit volume to powerthe associated electronic device for an acceptable period of time.Further, there is a limit to how small a crimped seal can be made; belowa certain size, it may not be possible to construct the coin cell atall.

U.S. Pat. No. 8,697,278 to Wyser et al. describes a coin cellconstruction having a metal lid and a metal base. The lid is anodized toform an insulation layer on selected portions thereof. This insulatingmaterial is then coated with a formable material, such as gold, and thelid is press-fitted to the metal base so that the anodized layer acts asan insulator between the opposite polarity base and lid while theformable material seals the anodized layer to the base. In this priorart cell construction, however, the sealing strength between theformable layer and the metal base may not be strong enough to withstandthe pressure of evolved gas or electrode expansion. This may cause thebase and lid to gradually separate from each other, resulting in leakageof electrolyte from the cell and loss of function.

Therefore, what is needed is an improved miniature electrochemical cellhaving a total volume that is less than 0.5 cc. The cell enclosure mustbe both mechanically robust and resistive to corrosion of the type thatcan occur when the cell is implanted in an animal or human body. Theminiature electrochemical cells of the present invention meet theseneeds.

SUMMARY OF THE INVENTION

Miniature electrochemical cells according to the present inventionemploy mechanically robust sealing approaches that are capable ofmaintaining hermeticity for 10 years, or more. A ceramic material servesas the insulating layer disposed between the anode and cathodeterminals. The insulating ceramic is joined to the opposite polarityterminals using a metal-containing feedthrough formed by co-firing ametallic paste in a via hole extending through a green ceramic.

In that respect, as with every cell, miniature electrochemical cellsaccording to the present invention have two terminals that areelectrically isolated from each other. However, in order for the cell tooperate for 10 years or more, novel robust sealing methodologies arerequired to prevent ingress of moisture or egress of electrolyte whilestill providing adequate electrical isolation between the terminals. Theproblem is that conventional sealing methods are often not practicalwhen cell sizes drop below 0.5 cc. That is because the seals themselvesbecome a major portion of the overall cell volume. On the other hand,the present invention describes multiple encapsulation methodologiesthat are designed to provide a miniature electrochemical cell having atotal volume of less than 0.5 cc with a hermetic seal exhibiting highvolumetric efficiency.

In addition, as cells become smaller and smaller, it becomes moredifficult to find space for the electrolyte fill port, and to find apractical means of plugging and sealing the fill port. The presentinvention describes a novel fill port design and hermetic fill portsealing process that is readily adapted to miniature electrochemicalcells having a total volume of less than 0.5 cc.

Moreover, with cell sizes below 0.5 cc, it may become advantageous touse a solid electrolyte so that filling with a liquid is not required.However, conventional solid electrolyte cells are known to undergoexpansion and contraction during cycling and consequently requirehermetic encapsulation structures that are designed to accommodate theexpected dimensional changes. Enclosure designs for miniature cellsactivated with solid electrolyte systems do not currently exist.Therefore, one aspect of the present invention is to provideencapsulation structures that can be applied to miniature solid-stateelectrochemical cells to provide a hermetic seal while accommodating therequired dimensional changes.

In the case of solid-state cells, ceramic substrates are well known inthe art, but are often formed with rough surfaces. Rough substratesurfaces can lead to defective coatings such as interruptedinterconnection traces, protrusions which may cause electric shortingbetween layers, uneven reaction leading to poor cycling or dendriteformation, and the like. Miniature solid-state electrochemical cellsaccording to the present invention use physical vapor deposition (PVD)for laying down the non-active layers, for example the anode and cathodecurrent collectors, onto ceramic substrates that have been lapped andpolished with slurry or ceramic coated grinding paper followed bydiamond polishing to a smooth surface finish.

Another problem with conventional miniature electrochemical cell designsis the need for the materials from which the cell is constructed to beboth chemically compatible with each other and not susceptible toundesirable corrosion reactions. In the case of a ceramic housing, aminiature electrochemical cell according to the present invention usesvarious electrically conductive materials in the form of a conductivepaste that is filled into a via hole extending through a ceramicplate-shaped substrate to thereby provide a hermetic feedthrough. Acurrent collector is then deposited on an inner surface of the lappedand polished ceramic substrate in contact with the via fill material. Inaddition to providing electrical conduction from the electrode activelayer to the via fill material, the current collector protects the fillmaterial from corrosive reactions with other battery components whileexhibiting good adhesion to the ceramic substrate or to an adhesionlayer on the substrate should there be one. Exemplary current collectorsaccording to the present invention are from about 0.1 microns to about50 microns thick and comprised of a metallic layer that is deposited onthe ceramic substrate using a PVD process so that the deposited metalcovers the via. Exemplary current collector materials include copper andtitanium.

Thus, the present invention describes various concepts for miniatureelectrochemical cells. The first cell concept relates to ahermetically-sealed electrochemical cell activated with either a liquidor a solid electrolyte. One or both of the anode and cathode terminalsconsist of a metal or metal/ceramic mixture surrounded by a ceramicsubstrate with the metal or metal/ceramic mixture being hermeticallybonded or sealed to the substrate. The bond is preferably formed byco-firing a metallic material filled into a via hole extending through agreen ceramic body. The metal is preferably platinum or aplatinum/ceramic composite and the ceramic is 3% YSZ or alumina.

A miniature electrochemical cell activated with a liquid electrolytecomprises a ceramic enclosure containing a secondary via serving as afill port. A metallic material is filled into the secondary via with anopen hole in the center of the fill material. After the cell is filledwith electrolyte, the metallic material in the electrolyte fill via ismelted, preferably using a laser, to form a hermetic seal. The metal ispreferentially platinum or platinum ceramic composite and the ceramic is3% YSZ or alumina.

A hermetically-sealed electrochemical cell comprises a ceramic lid and aceramic base. The lid and base are joined by welding a peripheral bandthat is attached to the ceramic by co-firing the band with the ceramicso that they are chemically-bonded together. Preferably, the metalperiphery band consists of platinum co-fired with a ceramic or acomposite of platinum/ceramic co-fired with additional filler metalsselected from gold, platinum, and palladium at the weld joint.

In the case of a miniature electrochemical cell according to the presentinvention that is activated with a solid electrolyte, the hermeticceramic enclosure is provided with a welded periphery and metallicfeedthroughs in which the bottom surface of the lid is between 1 and 100um above the upper surface of the cell stack. The gap between the cellstack and the lid provides sufficient space for dimensional changes tothe cell stack without damaging the enclosure or disrupting the seal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of a miniatureelectrochemical cell 10 according to the present invention.

FIG. 2 is a cross-sectional view of another embodiment of a miniatureelectrochemical cell 10A according to the present invention.

FIG. 3 is a cross-sectional view of another embodiment of a miniatureelectrochemical cell 100 according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A miniature electrochemical cell according to the present invention isnot limited to any particular type. The miniature electrochemical cellcan be an alkaline cell, a primary lithium cell, a rechargeable lithiumcell, a Ni/cadmium cell, a Ni/metal hydride cell, a supercapacitor, athin film solid-state cell, and the like. An exemplary miniatureelectrochemical cell is of a lithium-ion chemistry having a carbon-basedanode and a metal oxide-based cathode, such as a cathode of LiCoO₂ orLiNi_(a)Mn_(b)Co_(1-a-b)O₂, or a solid-state thin film cell with alithium anode, a metal-oxide based cathode and a solid electrolyte, forexample a LiPON (Li_(x)PO_(y)N_(z), with x ranging from 3 to 4, yranging from 3 to 4 and z ranging from 0.1 to 1)) electrolyte. If thecell is not of a solid-state chemistry, it is activated with a liquidelectrolyte. The liquid electrolyte is added to the cell stack prior tojoining the case and lid, or alternatively, a fill port is provided inthe metallic or ceramic casing so that the fill port and consequentiallythe casing can be hermetically sealed after filling with electrolyte.

Referring now to the drawings, FIG. 1 illustrates a first embodiment ofa miniature electrochemical cell 10 according to the present invention.The cell 10 comprises a first monolithic substrate or plate 12 of aceramic material, for example, of alumina that is spaced from a secondmonolithic substrate or plate 14 of a ceramic material, for example, ofalumina. According to one embodiment of the present invention, the firstand second substrates 12, 14 may be fabricated from a pressed ceramicslurry in tape form, which is widely available commercially. Alsoaccording to the present invention, a substrate of 92%-99% alumina(Al₂O₃) may be used for the ceramic substrates 12, 14. The substratematerial may be bought in sheet form, which may be flexible or rigid.

The first ceramic substrate 12 has a major sidewall 12A extending to anupper surface 12B and a lower surface 12C. The upper and lower surfaces12B, 12C are substantially co-planar. The major sidewall 12A is notlimited to any particular shape; it can have a curved annular shape orcomprise front and back sidewall portions meeting right and leftsidewall portions. As those skilled in the art will readily understand,a myriad of other shapes are contemplated for the major sidewall 12A ofthe first ceramic substrate 12, the shape being limited only by the formfactor for the particular application or device that the cell 10 isintended to power.

A depending annular portion 12D extends downwardly from the lowersurface 12C of the ceramic substrate 12. The annular portion 12Dcomprises an inner annular surface 12E spaced from an outer annularsurface 12F. Both annular surfaces 12E and 12F meet an annular face 12G.As shown, the annular portion 12D is spaced inwardly from the majorsidewall 12A.

The first ceramic substrate 12 has a first via hole 18 extending fromthe upper surface 12B to the lower surface 12C thereof. The first viahole 18 is provided with an electrically conductive pathway 20 thatextends to the spaced apart upper and lower ceramic substrate surfaces12B, 12C. The electrically conductive pathway 20 is formed by fillingthe via hole 18 with a ceramic reinforced metal composite or CRMC paste20A and then, in the green state, the inner diameter of the CRMC pasteis drilled out so that the via hole can be re-filled with asubstantially pure platinum paste, or a platinum wire 20B. In the caseof a substantially pure platinum paste 20B, the paste formulation issubstantially devoid of a ceramic material.

The second ceramic substrate 14 has a major sidewall 14A extending to anupper surface 14B that is substantially coplanar with a lower surface14C. In a similar manner as with the major sidewall 12A of the firstceramic substrate 12, the shape of the major sidewall 14A is not limitedto any particular form as it may have a myriad of shapes dictated by theform factor for the particular application or device that the cell 10 isintended to power. Preferably, however, the major sidewalls 12A, 14A ofthe respective first and second ceramic substrates 12, 14 have similarperipheral shapes.

An annular portion 14D extends upwardly from the upper surface 14B ofthe ceramic substrate 14. The upstanding annular portion 14D comprisesan inner annular surface 14E spaced from an outer annular surface 14F.Both annular surfaces 14E and 14F meet an annular face 14G. As shown,the annular portion 14D is spaced inwardly from the major sidewall 14A.

The second substrate 14 preferably comprises a monolithic aluminasubstrate that has a second via hole 22 extending from the upper surface14B to the lower surface 14C thereof. The second via hole 22 is providedwith a conductive pathway 24 that extends to the spaced apart upper andlower substrate surfaces 14B, 14C. Conductive pathway 24 is similar tothe conductive pathway 20 disposed through the first via hole 18 of thefirst ceramic substrate 12 and is comprised of a CRMC paste 24Asurrounding a cylinder of substantially pure platinum paste 24B. TheCRMC paste 24A is similar to the CRMC paste 20A and the platinumcylinder 24B is similar to the substantially pure platinum cylinder 20Bof the first conductive pathway 20.

The first ceramic substrate 12 also has a third via hole 26 extending tothe upper and lower surfaces 12B, 12C. However, instead of filling oroccupying the entire volume of the third via hole in a similar manner asthe first and second conductive pathways 20, 24 occupy the first andsecond via holes 18, 22 in the respective first and second ceramicsubstrates 12, 14, the third platinum fill 28 has the shape of a sleeveprovided with an opening 30 extending to the upper and lower surfaces12B, 12C. In that respect, the third via hole 26 is provided with anouter cylinder of CRMC paste 28A surrounding an inner cylinder ofsubstantially pure platinum paste 28B. As will be described in detailhereinafter, opening 30 serves as a passageway for filling anelectrolyte into the interior of the electrochemical cell 10.

Examples of CRMC ceramic/metal pairings include, but are not limited to:

a) Alumina (Al₂O₃) or zirconia (ZrO₂) including various stabilized orpartially stabilized zirconia like zirconia toughened alumina (ZTA) andalumina toughened zirconia (ATZ) with platinum (Pt) or palladium (Pd).

b. Alumina (Al₂O₃) or zirconia (ZrO₂) with iridium, rhenium, rhodium,various Pt alloys (e.g., Pt—Ir, Pt—Pd, Pt—Rh, Pt—Re, Pt—Au, Pt—Ag etc.),Pd alloys (e.g., Pd—Ir, Pd—Re, Pd—Rh, Pd—Ag, Pd—Au, Pd—Pt, Pd—Nb, etc.),Au alloys (e.g., Au—Nb, Au—Ti, etc.), Au alloys (e.g., Au—Nb, Au—Ti,etc.), and Ti alloys (e.g., Ti—Al—V, Ti—Pt, Ti—Nb, etc.)

Other non-limiting biocompatible metals and alloys that may be used inplace of platinum include niobium, platinum/palladium, stainless steels,and titanium.

Furthermore any of the following materials may be used alone or incombination with any of the materials already discussed or within thislist: gold (Au), silver (Ag), iridium (Ir), rhenium (Re), rhodium (Rh),titanium (Ti), tantalum (Ta), tungsten (W), zirconium (Zr), and vanadium(V); cobalt chromium molybdenum alloy, cobalt chromium nickel ironmolybdenum manganese alloy, cobalt chromium tungsten nickel ironmanganese alloy, cobalt nickel chromium iron molybdenum titanium alloy,cobalt nickel chromium iron molybdenum tungsten titanium alloy, cobaltnickel chromium molybdenum alloy, copper aluminum nickel alloy, copperzinc alloy, copper zinc aluminum nickel alloy, copper zinc silver alloy,gold platinum palladium silver indium alloy, iron chromium alloy, ironchromium nickel alloy, iron chromium nickel aluminum alloy, ironchromium nickel copper alloy, iron chromium nickel copper molybdenumniobium alloy, iron chromium nickel copper niobium alloy, iron chromiumnickel copper titanium niobium alloy, iron chromium nickel manganesemolybdenum alloy, iron chromium nickel molybdenum alloy, iron chromiumnickel molybdenum aluminum alloy, iron chromium nickel titaniummolybdenum alloy, iron manganese chromium molybdenum nitrogen alloy,nickel platinum alloy, nitinol, nickel titanium alloy, nickel titaniumaluminum alloy, niobium-titanium alloy, platinum iridium alloy, platinumpalladium gold alloy, titanium aluminum vanadium alloy, titanium basedaluminum iron alloy, titanium based aluminum molybdenum zirconium alloy,titanium based molybdenum niobium alloy, titanium based molybdenumzirconium iron alloy, titanium based niobium zirconium alloy, titaniumbased niobium zirconium tantalum alloy, titanium molybdenum alloy,titanium niobium alloy, titanium platinum alloy, and titanium-basedmolybdenum zirconium tin alloy.

It is understood that throughout this disclosure when CRMC paste andpure platinum paste are referred to, those pastes include solvents andbinders that will be baked out during sintering. Suitable binders areselected from the group consisting of ethyl cellulose, acrylic resin,polyvinyl alcohol, polyvinyl butyral and a poly(alkylene carbonate)having the general formula R—O—C(═O)—O with R═C1 to C5. Poly(ethylenecarbonate) or poly(propylene carbonate) are preferred poly(alkylenecarbonates). Suitable solvents are selected from the group consisting ofterpineol, butyl carbitol, cyclohexanone, n-octyl alcohol, ethyleneglycol, glycerol, water, and mixtures thereof.

In that respect, an important aspect of a miniature electrochemical cellaccording to the present invention centers around three enabling areas:(1) packing the ceramic substrate via holes 18, 22 and 26 with a highplatinum solids loading in the CRMC paste and in the platinum paste, (2)compression of the ceramic substrate against the CRMC paste and in turnthe CRMC paste against the platinum paste during binder bake-out andsintering, and (3) a controlled cool down rate in combination withinterfacial bonding sufficient to tolerate coefficient of thermalexpansion (CTE) mismatch. That is because metal/ceramic compatibility isan important factor in manufacturing hermetic structures. The differencein CTEs of the metal and ceramic is recognized as a major parameter inpredicting compatibility.

The thermal expansion of a metal is generally considerably greater thanthat of a ceramic material. For example, at a bake-out temperature of500° C., the CTE of alumina is 7.8×10⁻⁶/K and of platinum is 9.6×10⁻⁶/K.Historically, a CTE difference within the range of 0.5×10⁻⁶/K to1.0×10⁻⁶/K between the mating metal and ceramic material is adequate tosustain hermetic bonding between these materials. However, it isbelieved that a difference beyond that range at the bake-out temperaturefor the alumina/platinum pair may produce sufficient tensile stresses atthe interface during cooling to cause spontaneous bonding failure.Hence, given the significant difference in CTEs, even at a relativelylow temperature of 500° C., achieving a hermetic seal between theplatinum metal and alumina ceramic material would not be expected if thedifference in CTE between the sintered alumina and the platinum metalexceeds the range of 0.5×10⁻⁶/K to 1.0×10⁻⁶/K.

In addition, a highly irregular surface at the material interfacebetween the alumina substrate and the platinum metal particles withinthe via hole provides a mechanical contribution to adherence androbustness of the hermetic seal. A surface roughness produced by drillbits, sandblasting, grit blasting or chemical etching of the ceramicsubstrate can increase the surface area and, in so doing, provide for astronger mechanical attachment along the mutually conformal interface.Examples of sandblasting and grit blasting media include sand, sodiumbicarbonate, walnut shells, alumina particles, and other equivalentmedia.

According to the present invention, to achieve sustainable hermeticity,the following is required. Because the CTE of platinum is sufficientlyhigher than that of alumina, it is not theoretically possible foralumina to provide compressive forces on a platinum body in a via hole.Hence, to overcome the CTE differences between these two materials, theCRMC paste preferably has a ratio of alumina to platinum that ranges, byweight %, from about 10:90 to about 90:10, more preferably from about50:50, still further preferably 70:30 to 30:70.

The via holes 18, 22 and 26 through the alumina substrates 12, 14 mustbe packed with the CRMC paste to occupy at least about 90% of theavailable space. In a preferred embodiment, the CRMC paste is packed tooccupy about 95% of the via hole space. In a more preferred embodiment,the CRMC paste is packed to occupy about 99% of the via hole. The CRMCpaste is a smooth, soft mass having a pliable consistency and comprisingalumina particles, pure platinum particles, a binder material and asolvent.

Further, the platinum contacting the CRMC mixture in the via that waspreviously drilled through the CRMC material is a platinum pasteoccupying at least about 90% of the available space in the drilled CRMCvia hole. In a preferred embodiment, the platinum paste is packed withinthe CRMC via to occupy about 95% of the space. In a more preferredembodiment, the platinum paste is packed to occupy about 99% of the CRMCvia. In the case of the substantially pure platinum, a “paste” isdefined as a smooth, soft mass having a pliable consistency andcomprising pure platinum particles, a binder material and a solvent.

Moreover, shrinkage of the alumina substrate against the CRMC mixtureand of the alumina in the CRMC mixture against the platinum paste mustbe no greater than about 20% of that of the platinum in the via hole. Ina preferred embodiment, shrinkage is about 14%. In a more preferredembodiment, shrinkage is about 16%.

Importantly, the CRMC mixture 20A closely matches the thermalcoefficient of expansion of the alumina substrate 12. This results in avery good hermetic seal between the CRMC mixture 20A and the aluminasubstrate 12 and between the CRMC mixture 20A and the cylinder ofsubstantially pure platinum 20B. Further, the CRMC mixture 20A whichsurrounds the pure platinum cylinder 20B forms a buffer during sinteringand subsequent thermal shock so that there is a gradation of thedifferential and thermal coefficient of expansion. The thickness of theCRMC paste 20A can be adjusted along with the diameter of the pureplatinum cylinder 20B so that during co-firing no stress cracks areinduced in the ceramic substrate 12.

The electrode assembly of the cell 10 comprises an anode currentcollector 32 seated against the lower surface 12C of the upper substrate12. An anode active material 34 contacts the opposite side of thecurrent collector 32. Similarly, a cathode current collector 36 isseated against the upper surface 14B of the lower substrate 14. Acathode active material 38 is contacted to the opposite side of thecathode current collector 36. An alumina spacer 40 serving as aseparator resides between the anode and the cathode active materials 34,38. Preferably, the separator 40 is in direct contact with the anodeactive material 34 and the cathode active material 38 opposite theirrespective current collectors 32, 26. That way, the separator 40prevents direct physical contact between the anode active material 34and the cathode active material 38 while allowing for ionic transportand conductivity therebetween.

An optional weld band 42 surrounds the electrode assembly comprising thestacked anode current collector 32, anode active material 34, separator40, cathode active material 38 and cathode current collector 36. Anupper edge 42A of the weld band 42 contacts the lower surface 12C of thefirst substrate 12 while a lower edge 42B thereof contacts the uppersurface 14B of the second substrate 14.

An annular air space 44 resides between the weld band 42 and theperipheral edges of the anode and cathode current collectors 32, 36,anode active material 34, cathode active material 38 and theintermediate separator 40. Opposite the annular air space, the weld band42 contacts the depending and upstanding portions 12D and 14D of therespective first and second substrate 12, 14.

An upper annular ring 46 of CRMC paste surrounds the depending portion12D of the first substrate 12 while a lower annular ring 48 of CRMCpaste surrounds the upstanding portion 14D of the second ceramicsubstrate 14. The upper and lower annular rings 46 and 48 are spacedinwardly from the major sidewalls 12A and 14A of the respective ceramicsubstrates 12, 14. This provides a space for an upper annular ring 50 ofa substantially pure platinum paste that surrounds the upper annularring 46 of CRMC paste. Similarly, a lower annular ring 52 of asubstantially pure platinum paste surrounds the lower annular ring 48 ofCRMC paste. The pairs of the depending and upstanding ceramic portions12D and 14D, the upper and lower CRMC rings 46 and 48, and the upper andlower substantially pure platinum rings 50 and 52 meet each other atrespective interfaces that are aligned with each other.

In that manner, the miniature electrochemical cell 10 is constructed byfirst positioning the CRMC rings 46 and 48 followed by the substantiallypure platinum rings 50 and 52 into position with the respective ceramicsubstrates 12 and 14, all in a green state. The first and third viaholes 18 and 26 are provided with their respective CRMC and platinumstructures in a green state. Similarly, the second via hole 22 of thesecond ceramic substrate 14 is provided with its CRMC and platinumstructure in a green state.

After the ceramic substrate subassemblies 12, 14 including their filledvia holes 18, 22 and 26, respective CRMC rings 46, 48 and respectivesubstantially pure platinum rings 50 and 52 are assembled, the substratesubassemblies are subjected to a controlled binder bake-out, sinteringand cool down processing profile. The binder bake-out portion isperformed at a temperature of from about 400° C. to about 700° C. for aminimum of about 4 hours. A preferred binder bake-out is at atemperature of from about 550° C. to about 650° C. A more preferredbinder bake-out is at a temperature of from about 500° C. to about 600°C.

The sintering profile is preferably performed at a temperature rangingfrom about 1,400° C. to about 1,900° C. for up to about 6 hours. Apreferred sintering profile is at a temperature ranging from about1,500° C. to about 1,800° C. A more preferred sintering temperatureranges from about 1,600° C. to about 1,700° C.

The cool down profile occurs either by turning off the heating chamberand allowing the chamber to equalize to room temperature or, preferablyby setting the cool down portion at a rate of up to about 5° C./min fromthe hold temperature cooled down to about 1,000° C. At about 1,000° C.,the chamber is allowed to naturally equalize to room temperature. A morepreferred cool down profile is at a rate of about 1° C./min from thehold temperature to about 1,000° C. followed by allowing the heatingchamber to naturally equalize to room temperature. In so doing, thedesired outcome of achieving a robust hermetic seal is achieved betweenthe mating materials of the alumina and platinum. It is noted that thesematerials have a CTE mismatch beyond the limits heretofore recognized asadequate for sustained bonding.

During processing, compression is imparted by the alumina substratearound the CRMC paste and in turn the CRMC paste against the platinumpaste within the via due to the shrinkage of the alumina being greaterthan that of the CRMC mixture and the shrinkage of the CRMC mixturebeing greater than that of the substantially pure platinum. Furthermore,the platinum is sufficiently malleable at this phase to be favorablydeformed by the compressive forces being applied by the alumina in thesubstrates 12, 14 and in the CRMC paste. The combination of the platinumsolids loading, the platinum packing in the via hole and the shrinkageof the alumina being greater than that of platinum results in theplatinum taking the shape of the mating CRMC surface and in turn theCRMC surface taking the shape of the alumina substrate surface.

In other words, the compressive forces that result from the greatershrinkage of the alumina substrate than that of the CRMC mixture and inturn the shrinkage of the CRMC mixture being greater than that of theplatinum within the via holes 18, 22 and 26 limit expansion of theplatinum and force the platinum to deform such that it forms a hermeticseal. Thus, an interface between the alumina and CRMC mixture andbetween the CRMC mixture and the platinum material that conform to therespective interface surfaces and result in a nearly exact mirror imageof the interfacing surfaces is formed, thereby creating a hermetic bondtherebetween. This mutually conformal interface is critical.

Under certain processing conditions CRMC bodies may form a thin glasslayer or even an alumina layer over the via ends. It may be necessarytherefore to remove this formed layer with an additional manufacturingstep, such as acid etch, lapping or mechanical abrasion.

After the substrate subassemblies 12, 14 have been subjected to thebinder bake-out, sintering and cool down processing, the optional weldband 42 is positioned into one of the upper and lower ceramic substrates12, 14. The electrode assembly comprising the previously described anodecurrent collector, 32, anode active material 34, separator 40, cathodeactive material 38 and cathode current collector 36 is nested inside theweld band 42. The other of the upper and lower ceramic substrate 12, 14is then moved into position so that their respective annular faces 12Gand 14G contact each other. A laser (not shown) is then used to direct alaser beam at the annular interface between the pure platinum rings 50and 52. This serves to melt the platinum material in the rings and alsopossibly melt the platinum in the CRMC rings 46 and 48 to therebyhermetically seal the ceramic subassemblies 12 and 14 together. Ifdesired, the laser beam can also be directed at the annular interfacebetween the upper platinum ring 50 and the upper ceramic substrate 12and at the annular interface between the lower platinum ring 52 and thelower ceramic substrate 14.

The electrode assembly housed inside the hermetically seal ceramicsubassemblies 12 and 14 is then activated with an electrolyte filledthrough the fill opening 30 in the third via hole 26 in the uppersubstrate 12. Finally, a hermetic electrochemical cell 10 is provided bysealing the fill opening 30 with a laser beam in a similar manner aspreviously described with respect to sealing the ceramic subassemblies12 and 14 together with a laser beam directed at the annular interfacebetween the platinum rings 50, 52.

The electrochemical cell 10A illustrated in FIG. 2 is similar to thecell 10 shown in FIG. 1 except that the depending portion 12D of theceramic substrate 12 and the upstanding portion 14D of the lower ceramicsubstrate do not abut or contact each other. Instead, they are spacedapart from each other. Similarly, the respective CRMC rings 46A and 48A,and the respective platinum rings 50A and 52A are spaced apart from eachother. An annular disc 54 of a precious metal, for example a discselected from gold, platinum and palladium resides in this gap. A laserbeam is directed at the precious metal disc 54 to fuse the disc to theplatinum rings 50A, 52A and to the CRMC rings 46A, 48A to thereby sealthe upper and lower ceramic subassemblies 12 and 14 together.

An activating electrolyte is filled through the fill hole 30 intocontact with the electrode assembly housed therein and the fill hole issealed with a laser beam as previously described.

FIG. 3 illustrates another embodiment of a miniature electrochemicalcell 100 according to the present invention. The cell 100 comprises afirst monolithic substrate or plate 102 of a ceramic material, forexample, of alumina that is spaced from a second monolithic substrate orplate 104 of a ceramic material, for example, of alumina. In a similarmanner as the various substrates described for the electrochemical cells10 and 10A illustrated in FIGS. 1 and 2, the first and secondsubstrates. 102, 104 may be fabricated from a pressed ceramic slurry intape form, for example 92%-99% alumina (Al₂O₃). The substrate materialmay be flexible or rigid.

The first ceramic substrate 102 has a major sidewall 102A extending toan upper surface 102B and a lower surface 102C. The upper and lowersurfaces 102B, 102C are substantially co-planar. The major sidewall 102Ais not limited to any particular shape; it can have a curved annularshape or comprise front and back sidewall portions meeting right andleft sidewall portions. In fact, a myriad of other shapes arecontemplated for the major sidewall 102A of the first ceramic substrate102, the shape being limited only by the form factor for the particularapplication or device that the cell 100 is intended to power.

A depending annular portion 102D extends downwardly from the lowersurface 102C of the ceramic substrate 102. The annular portion 102Dcomprises an inner annular surface 102E spaced from an outer annularsurface 102F. Both annular surfaces 102E and 102F meet an annular face102G. As shown, the annular portion 102D is spaced inwardly from themajor sidewall 102A.

The second ceramic substrate 104 has a first sidewall 104A extending toan upper surface 104B and a lower surface 104C. The upper and lowersurfaces 104B, 104C are substantially co-planar. The second ceramicsubstrate 104 further has a second sidewall 104D extending to an uppersurface 104E and a lower surface 104F. The upper and lower surfaces104E, 104F are substantially co-planar. Moreover, the upper surface 104Emeets the first sidewall 104A as a monolithic structure. Importantly,the second sidewall 104D is spaced outwardly from the first sidewall104A to thereby form an annular ledge where the second upper surface104E meets the first sidewall 104A. The second annular sidewall 104D issubstantially aligned with the first sidewall 102A of the firstsubstrate 102.

The second substrate 104 preferably comprises a monolithic aluminasubstrate that has a first via hole 106 and a second via hole 108, bothextending from the upper surface 104B to the lower surface 104C thereof.The via holes 106 and 108 are provided with respective conductivepathways 110 and 112 that each extend to the spaced apart upper andlower second substrate surfaces 104B and 104C. The conductive pathway108 residing in the via hole 106 comprises a CRMC paste 110A contactingthe alumina substrate 104 and a substantially pure platinum paste 110Bdisposed inside a via hole drilled through the CRMC paste. Similarly,the conductive pathway 112 residing in the second via hole 108 comprisesa CRMC paste 112A contacting the alumina substrate 104 and asubstantially pure platinum paste 112B disposed inside a via holedrilled through the CRMC paste. This is in a similar manner as thepreviously described conductive pathways 20 and 24 illustrated in FIGS.1 and 2 for electrochemical cells 10 and 10A.

The electrode assembly of the cell 100 comprises a cathode currentcollector 114 seated against the upper surface 104B of the lowersubstrate 104 aligned with the first via hole 106. An anode currentcollector 116 is seated against the upper surface 104B of the lowersubstrate aligned with the second via hole 108. In their alignedorientations, the cathode current collector 114 contacts the platinum110B in via hole 106 and the anode current collector 116 contacts theplatinum 112B in via hole 108.

A cathode active material 118 contacts the cathode current collector 114opposite the platinum 110B in via hole 106. A separator 120 has anannular shape in plain view with a recess 1120A that is sized and shapedto receive the cathode active material 118 supported on the cathodecurrent collector 114. An outer annular edge 120B of the separatorcontacts or is otherwise supported on the upper surface 104B of thesecond substrate 104.

A shaped anode 122 contacts the anode current collector 116 opposite theplatinum material 112B in the via hole 108. The anode active material122 also contacts the separator 120. In that respect, the anode 122 hasa curved sidewall 122A extending to an upper surface 122B. A shapedlower surface 122C opposite the upper surface 112B contacts the anodecurrent collector 116 and separator 120 to thereby provide the anodewith a backwards and sideways L-shape in cross-section.

An exemplary chemistry for the miniature electrochemical cell 100 shownin FIG. 3 has lithium as an exemplary anode active material, LiCoO₂ as acathode active material and the separator is of LiPON(Li_(x)PO_(y)N_(z), with x ranging from 3 to 4, y ranging from 3 to 4and z ranging from 0.1 to 1). LiPON is a solid material that both servesas both the separator and the electrolyte for the Li/LiCoO₂ couple.

An optional weld band 124 surrounds the side-by-side anode 122 andcathode 118 including their respective current collectors 116, 114 andthe intermediate separator 118. In that respect, an upper edge 124A ofweld band 124 contacts a lower surface 102C of the upper substrate 102while a lower edge 124B of the band rests on the upper surface 104B ofthe lower substrate 104. An outer surface 124C of the weld band isspaced inwardly from the peripheral sidewalls 102D of the firstsubstrate 102. An air gap 126 resides between the weld band 124 and theelectrode assembly.

An upper annular ring 126 of CRMC paste surrounds the depending portion102D of the first substrate 102 while a lower annular ring 128 of CRMCpaste surrounds the sidewall 104A of the second ceramic substrate 104.The upper and lower annular rings 126 and 128 are spaced inwardly fromthe sidewalls 102A and 104D of the respective ceramic substrates 102,104. This provides a space for an upper annular ring 130 of asubstantially pure platinum paste that surrounds the upper annular ring126 of CRMC paste. Similarly, a lower annular ring 132 of asubstantially pure platinum paste surrounds the lower annular ring 128of CRMC paste. The pairs of the depending and upstanding ceramicportions 102D and 104A, the upper and lower CRMC rings 126 and 128, andthe upper and lower substantially pure platinum rings 130 and 132 meeteach other at respective interfaces that are aligned with each other.

In that manner, the miniature electrochemical cell 100 is constructed byfirst positioning the CRMC rings 126 and 128 followed by thesubstantially pure platinum rings 130 and 132 into position with therespective ceramic substrates 102 and 104, all in a green state. Thefirst and second via holes 108 and 106 are provided with theirrespective CRMC and platinum structures in a green state.

After the ceramic substrate subassemblies 102, 104 including theirfilled via holes 106 and 108, respective CRMC rings 126, 128 andrespective substantially pure platinum rings 130 and 132 are assembled,the substrate subassemblies are subjected to a controlled binderbake-out, sintering and cool down processing profile as previouslydescribed with respect to electrochemical cells 10 and 10A.

After binder bake-out, sintering and cool down processing, the optionalweld band 124 is positioned in one of the upper and lower ceramicsubstrates 102, 104, preferably the lower substrate. The electrodeassembly comprising the previously described anode current collector116, anode active material 122, separator 120, cathode active material118 and cathode current collector 114 is nested inside the weld band124. The other of the upper and lower ceramic substrate 102, 104,preferably the upper substrate, is then moved into position so thattheir respective annular surfaces 102G and 104B contact each other. Alaser (not shown) is then used to direct a laser beam at the annularinterface between the pure platinum rings 130 and 132. This serves tomelt the platinum material in the rings and also possibly melt theplatinum in the CRMC rings 126 and 128 to thereby hermetically seal theceramic subassemblies 102 and 104 together. If desired, the laser beamcan also be directed at the annular interface between the upper platinumring 130 and the upper ceramic substrate 102 and at the annularinterface between the lower platinum ring 132 and the lower ceramicsubstrate 104.

In a broad sense, the miniature electrochemical cells 10, 10A and 100can each be of a primary or a secondary chemistry. If a primarychemistry, the anode can also comprise metals capable of alloying withlithium at potentials below 1.0 V vs. lithium such as Sn, Si, Al, B,Si—B, and composites of those metals with inactive metals to reducevolume expansion. The form of the anode may vary, but preferably it isof a thin sheet or foil that is pressed, evaporation, or rolled on themetallic anode current collector.

The cathode of a primary cell is of electrically conductive material,preferably a solid material. The solid cathode may comprise a metalelement, a metal oxide, a mixed metal oxide, and a metal sulfide, andcombinations thereof. A preferred cathode active material is selectedfrom the group consisting of silver vanadium oxide, copper silvervanadium oxide, manganese dioxide, cobalt nickel, nickel oxide, copperoxide, copper sulfide, iron sulfide, iron disulfide, titanium disulfide,copper vanadium oxide, carbon monofluoride, and mixtures thereof.

Before fabrication into an electrode for incorporation into anelectrochemical cell, the cathode active material is mixed with a bindermaterial such as a powdered fluoro-polymer, more preferably powderedpolytetrafluoroethylene or powdered polyvinylidene fluoride (PVDF)present at about 1 to about 5 weight percent of the cathode mixture.Further, up to about 10 weight percent of a conductive diluent ispreferably added to the cathode mixture to improve conductivity.Suitable materials for this purpose include acetylene black, carbonblack and/or graphite or a metallic powder such as powdered nickel,aluminum, titanium and stainless steel. The preferred cathode activemixture for the electrochemical cells 10 and 10A, but not for cell 100thus includes a powdered fluoro-polymer binder present at about 3 weightpercent, a conductive diluent present at about 3 weight percent, andabout 94 weight percent of the cathode active material.

The primary electrochemical cells 10 and 10A include a nonaqueous,ionically conductive electrolyte having an inorganic, ionicallyconductive salt dissolved in a nonaqueous solvent and, more preferably,a lithium salt dissolved in a mixture of a low viscosity solvent and ahigh permittivity solvent. The salt serves as the vehicle for migrationof the anode ions to intercalate or react with the cathode activematerial and suitable salts include LiPF₆, LiBF₄, LiAsF₆, LiSbF₆,LiClO₄, LiO₂, LiAlCl₄, LiGaCl₄, LiC(SO₂CF₃)₃, LiN(SO₂CF₃)₂, LiSCN,LiO₃SCF₃, LiC₆ F₅SO₃, LiO₂CCF₃, LiSO₆F, LiB(C₆H₅)₄, LiCF₃SO₃, andmixtures thereof.

Suitable low viscosity solvents include esters, linear and cyclic ethersand dialkyl carbonates such as tetrahydrofuran (THF), methyl acetate(MA), diglyme, trigylme, tetragylme, dimethyl carbonate (DMC),1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE),1-ethoxy,2-methoxyethane (EME), ethyl methyl carbonate, methyl propylcarbonate, ethyl propyl carbonate, diethyl carbonate, dipropylcarbonate, and mixtures thereof. High permittivity solvents includecyclic carbonates, cyclic esters and cyclic amides such as propylenecarbonate (PC), ethylene carbonate (EC), butylene carbonate,acetonitrile, dimethyl sulfoxide, dimethyl, formamide, dimethylacetamide, γ-valerolactone, γ-butyrolactone (GBL),N-methyl-pyrrolidinone (NMP), and mixtures thereof. The preferredelectrolyte for a lithium primary cell is 0.8M to 1.5M LiAsF₆ or LiPF₆dissolved in a 50:50 mixture, by volume, of PC as the preferred highpermittivity solvent and DME as the preferred low viscosity solvent.

By way of example, in an illustrative electrochemical cell, the activematerial of the cathode is silver vanadium oxide as described in U.S.Pat. Nos. 4,310,609 and 4,391,729 to Liang et al., or copper silvervanadium oxide as described in U.S. Pat. Nos. 5,472,810 and 5,516,340 toTakeuchi et al., all assigned to the assignee of the present invention,the disclosures of which are hereby incorporated by reference.

In the exemplary secondary electrochemical cell 100, in addition tolithium, the anode 122 can comprise a material capable of intercalatingand de-intercalating an alkali metal, and preferably lithium. Acarbonaceous anode comprising any of the various forms of carbon (e.g.,coke, graphite, acetylene black, carbon black, glassy carbon, etc.),which are capable of reversibly retaining the lithium species, ispreferred. Graphite is particularly preferred due to its relatively highlithium-retention capacity. Regardless of the form of the carbon, fibersof the carbonaceous material are particularly advantageous because theyhave excellent mechanical properties that permit them to be fabricatedinto rigid electrodes capable of withstanding degradation duringrepeated charge/discharge cycling.

The cathode 118 of the exemplary secondary electrochemical cell 100preferably comprises a lithiated material that is stable in air andreadily handled. Examples of such air-stable lithiated cathode materialsinclude oxides, sulfides, selenides, and tellurides of such metals asvanadium, titanium, chromium, copper, molybdenum, niobium, iron, nickel,cobalt and manganese. The more preferred oxides include LiNiO₂, LiMn₂O₄,LiCoO₂, LiCo_(0.92)Sn_(0.08)O₂, LiCo_(1-x) Ni_(x)O₂, LiFePO₄,LiNi_(x)Mn_(y)Co_(1-x-y)O₂, and LiNi_(x)Co_(y)Al_(1-x-y)O₂.

For electrochemical cells 10 and 10A, the lithiated active material ispreferably mixed with a conductive additive selected from acetyleneblack, carbon black, graphite, and powdered metals of nickel, aluminum,titanium and stainless steel. The cathode further comprises afluoro-resin binder, preferably in a powder form, such as PTFE, PVDF,ETFE, polyamides and polyimides, and mixtures thereof.

The respective current collectors are selected from stainless steel,titanium, tantalum, platinum, gold, aluminum, cobalt nickel alloys,highly alloyed ferritic stainless steel containing molybdenum andchromium, and nickel-, chromium- and molybdenum-containing alloys.

Suitable secondary electrochemical systems are comprised of nonaqueouselectrolytes of an inorganic salt dissolved in a nonaqueous solvent andmore preferably an alkali metal salt dissolved in a quaternary mixtureof organic carbonate solvents comprising dialkyl (non-cyclic) carbonatesselected from dimethyl carbonate (DMC), diethyl carbonate (DEC),dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propylcarbonate (MPC), and ethyl propyl carbonate (EPC), and mixtures thereof,and at least one cyclic carbonate selected from propylene carbonate(PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylenecarbonate (VC), and mixtures thereof. Organic carbonates are generallyused in the electrolyte solvent system for such battery chemistriesbecause they exhibit high oxidative stability toward cathode materialsand good kinetic stability toward anode materials.

Whether of a primary or a secondary chemistry, the cells 10 and 10A arefilled with the appropriate electrolyte described hereinabove andhermetically sealed such as by close-welding the fill openings 30 usinga laser beam.

Now, it is therefore apparent that the present invention relates tovarious embodiments for miniature electrochemical cells having a totalvolume of less than 0.5 cc. Moreover, while embodiments of the presentinvention have been described in detail, such is for the purpose ofillustration, not limitation.

What is claimed is:
 1. An electrochemical cell, comprising: a) a casing,comprising: i) a first ceramic substrate comprising opposed firstsubstrate inner and outer surfaces; ii) a second ceramic substratecomprising opposed second substrate inner and outer surfaces; and iii) aprecious metal disc hermetically sealing the first and second ceramicsubstrates together to provide the casing; and b) an electrode assemblyhoused inside the casing, the electrode assembly comprising: i) an anodeactive material contacting an anode current collector; ii) a cathodeactive material contacting a cathode current collector; and iii) aseparator disposed between the anode and cathode active materials; andc) a first conductive pathway extending through the first ceramicsubstrate and comprising first conductive pathway inner and outersurfaces located at or adjacent to the respective first ceramicsubstrate inner and outer surfaces; d) a second conductive pathwayextending through the second ceramic substrate and comprising secondconductive pathway inner and outer surfaces located at or adjacent tothe respective second ceramic substrate inner and outer surfaces, e)wherein the first conductive pathway inner surface is in an electricallyconductive relationship with one of the anode and cathode currentcollectors, and wherein the second conductive pathway inner surface isin an electrically conductive relationship with the other of the anodeand cathode current collectors, and f) wherein the respective first andsecond conductive pathway outer surfaces are configured for electricalconnection to a load; and g) an electrolyte inside the casing in contactwith the electrode assembly.
 2. The electrochemical cell of claim 1,wherein the first conductive pathway comprises a first via holeextending through the first ceramic substrate, a first ceramic/platinummixture disposed in the first via hole in a sealed relationship with thefirst ceramic substrate, and a first substantially pure platinum bodydisposed in a sealed relationship extending through the firstceramic/platinum mixture opposite the first ceramic substrate.
 3. Theelectrochemical cell of claim 1, wherein the second conductive pathwaycomprises a second via hole extending through the second ceramicsubstrate, a second ceramic/platinum mixture disposed in the second viahole in a sealed relationship with the second ceramic substrate, and asecond substantially pure platinum body disposed in a sealedrelationship extending through the second ceramic/platinum mixtureopposite the second ceramic substrate.
 4. The electrochemical cell ofclaim 1, wherein: a) a first substrate depending wall extends downwardlyand annularly from the first substrate inner surface, the firstsubstrate depending wall comprising a first depending wall outer annularface spaced from the first substrate inner surface; and b) a secondsubstrate upstanding wall extends upwardly and annularly from the secondsubstrate inner surface, the second substrate upstanding wall comprisinga second upstanding wall outer annular face spaced from the secondsubstrate inner surface, c) wherein the precious metal disc contacts thefirst and second outer annular faces of the respective depending andupstanding walls to hermetically seal the first and second ceramicsubstrates together.
 5. The electrochemical cell of claim 4, wherein theopposed first substrate inner and outer surfaces extend to a firstsubstrate outer annular edge, the first substrate depending wall beingspaced inwardly from the first substrate outer annular edge, and whereinthe opposed second substrate inner and outer surfaces extend to a secondsubstrate outer annular edge, the second substrate upstanding wall beingspaced inwardly from the second substrate outer annular edge, theelectrochemical cell further comprising: a) a first ring of a firstsintered ceramic/platinum mixture contacting the first substrate innersurface and an outer surface of the first substrate depending wall, thefirst ring having a first ring outer face aligned with the firstdepending wall outer annular face, and wherein a second ring of a secondsintered substantially pure platinum contacts an outer surface of thefirst ring, the second ring having a second ring outer face aligned withthe first ring outer annular face and the depending wall outer annularface; and b) a third ring of a third sintered ceramic/platinum mixturecontacting the second substrate inner surface and an outer surface ofthe second substrate upstanding wall, the third ring having a third ringouter face aligned with the second upstanding wall outer annular face,and wherein a fourth ring of sintered substantially pure platinumcontacts an outer surface of the third ring, the fourth ring having afourth ring outer face aligned with the third ring outer face and theupstanding wall outer annular face, c) wherein the precious metal discfurther contacts the second and fourth outer faces of the respectivesecond and fourth rings of the sintered substantially pure platinum andthe first and third outer faces of the respective first and third ringsof the sintered ceramic/platinum mixtures.
 6. The electrochemical cellof claim 5, wherein the first and third rings of the respective firstand third sintered ceramic/platinum mixtures are further characterizedas having been welded to the respective first and second ceramicsubstrates spaced from the precious metal disc hermetically sealing thefirst and second ceramic substrates together, and wherein the second andfourth rings of the substantially pure platinum are characterized ashaving been welded to the respective first and second ceramic substratesspaced from the precious metal disc hermetically sealing the first andsecond ceramic substrates together.
 7. The electrochemical cell of claim1, wherein the precious metal disc hermetically sealing the first andsecond ceramic substrates together is selected from the group of gold,platinum, and palladium.
 8. The electrochemical cell of claim 1, whereina third via hole extends through one of the first and second ceramicsubstrates, and wherein a third sintered ceramic/platinum mixture isdisposed in the third via hole in a sealed relationship with the one ofthe first and second ceramic substrates, and a third sinteredsubstantially pure platinum sleeve is disposed in a sealed relationshipextending through the third ceramic/platinum mixture opposite the one ofthe first and second ceramic substrates, and wherein the third sinteredsubstantially pure platinum sleeve is characterized as having beenwelded closed.
 9. The electrochemical cell of claim 8, wherein thefirst, second and third sintered ceramic/platinum mixtures individuallycomprise, by weight %, from 10:90 ceramic:platinum to 90:10ceramic:platinum.
 10. The electrochemical cell of claim 9, wherein thefirst, second and third sintered ceramic/platinum mixtures individuallycomprise, by weight %, from 70:30 ceramic:platinum to 30:70ceramic:platinum.
 11. The electrochemical cell of claim 1, wherein thefirst and second ceramic substrates are individually selected fromalumina and 3% YSZ.
 12. The electrochemical cell of claim 1, wherein theelectrode assembly is of either a primary or a secondary chemistry. 13.An electrochemical cell, comprising: a) a casing, comprising: i) a firstceramic substrate comprising opposed first substrate inner and outersurfaces, wherein a first substrate annular wall extends outwardly fromthe first substrate inner surface; ii) a second ceramic substratecomprising opposed second substrate inner and outer surfaces, wherein asecond substrate annular wall extends outwardly from the secondsubstrate inner surface; and iii) a precious metal disc hermeticallysealing the first and second outwardly extending annular walls of therespective first and second ceramic substrates together to provide thecasing; and b) an electrode assembly housed inside the casing, theelectrode assembly comprising: i) an anode active material contacting ananode current collector; ii) a cathode active material contacting acathode current collector; and iii) a separator disposed between theanode and cathode active materials; and c) a first conductive pathwayextending through the first ceramic substrate and comprising firstconductive pathway inner and outer surfaces located at or adjacent tothe respective first ceramic substrate inner and outer surfaces; d) asecond conductive pathway extending through the second ceramic substrateand comprising second conductive pathway inner and outer surfaceslocated at or adjacent to the respective second ceramic substrate innerand outer surfaces, e) wherein the first conductive pathway innersurface is in an electrically conductive relationship with one of theanode and cathode current collectors, and wherein the second conductivepathway inner surface is in an electrically conductive relationship withthe other of the anode and cathode current collectors, and f) whereinthe respective first and second conductive pathway outer surfaces areconfigured for electrical connection to a load; and g) an electrolyteinside the casing in contact with the electrode assembly.
 14. Theelectrochemical cell of claim 13, wherein: a) the first conductivepathway comprises a first via hole extending through the first ceramicsubstrate, a first sintered ceramic/platinum mixture disposed in thefirst via hole in a sealed relationship with the first ceramicsubstrate, and a first sintered substantially pure platinum bodydisposed in a sealed relationship extending through the first sinteredceramic/platinum mixture opposite the first ceramic substrate; and b)the second conductive pathway comprises a second via hole extendingthrough the second ceramic substrate.
 15. The electrochemical cell ofclaim 13, wherein the precious metal disc hermetically sealing the firstand second outwardly extending annular walls of the respective first andsecond ceramic substrates together is selected from the group of gold,platinum, and palladium.
 16. The electrochemical cell of claim 13,wherein the second conductive pathway comprises a second via holeextending through the second ceramic substrate, a second sinteredceramic/platinum mixture disposed in the second via hole in a sealedrelationship with the second ceramic substrate, and a second sinteredsubstantially pure platinum body disposed in a sealed relationshipextending through the second sintered ceramic/platinum mixture oppositethe second ceramic substrate.
 17. The electrochemical cell of claim 13,wherein a third via hole extends through one of the first and secondceramic substrates, and wherein a third sintered ceramic/platinummixture is disposed in the third via hole in a sealed relationship withthe one of the first and second ceramic substrates, and a third sinteredsubstantially pure platinum sleeve is disposed in a sealed relationshipextending through the third ceramic/platinum mixture opposite the one ofthe first and second ceramic substrates, and wherein the third sinteredsubstantially pure platinum sleeve is characterized as having beenwelded closed.
 18. The electrochemical cell of claim 17, wherein thefirst, second and third sintered ceramic/platinum mixtures individuallycomprise, by weight %, from 10:90 ceramic:platinum to 90:10ceramic:platinum.
 19. The electrochemical cell of claim 18, wherein thefirst, second and third sintered ceramic/platinum mixtures individuallycomprise, by weight %, from 70:30 ceramic:platinum to 30:70ceramic:platinum.
 20. The electrochemical cell of claim 13, wherein thefirst and second ceramic substrates are individually selected fromalumina and 3% YSZ.
 21. The electrochemical cell of claim 13, whereinthe electrode assembly is of either a primary or a secondary chemistry.22. An electrochemical cell, comprising: a) a casing, comprising: i) afirst ceramic substrate comprising opposed first substrate inner andouter surfaces, wherein a first substrate annular wall extends outwardlyfrom the first substrate inner surface; ii) a second ceramic substratecomprising opposed second substrate inner and outer surfaces; and iii) aprecious metal disc hermetically sealing the first substrate annularwall to the second ceramic substrate to provide the casing; and b) anelectrode assembly housed inside the casing, the electrode assemblycomprising: i) an anode active material contacting an anode currentcollector; ii) a cathode active material contacting a cathode currentcollector; and iii) a separator disposed between the anode and cathodeactive materials; and c) a first conductive pathway extending throughthe first ceramic substrate and comprising first conductive pathwayinner and outer surfaces located at or adjacent to the respective firstsubstrate inner and outer surfaces; d) a second conductive pathwayextending through the second ceramic substrate and comprising secondconductive pathway inner and outer surfaces located at or adjacent tothe respective second substrate inner and outer surfaces, e) wherein thefirst conductive pathway inner surface is in an electrically conductiverelationship with one of the anode and cathode current collectors, andwherein the second conductive pathway inner surface is in anelectrically conductive relationship with the other of the anode andcathode current collectors, and f) wherein the respective first andsecond conductive pathway outer surfaces are configured for electricalconnection to a load; and g) an electrolyte inside the casing in contactwith the electrode assembly.
 23. The electrochemical cell of claim 22,wherein the first conductive pathway comprises a first via holeextending through the first ceramic substrate, a first ceramic/platinummixture disposed in the first via hole in a sealed relationship with thefirst ceramic substrate, and a first substantially pure platinum bodydisposed in a sealed relationship extending through the firstceramic/platinum mixture opposite the first ceramic substrate.
 24. Theelectrochemical cell of claim 22, wherein the second conductive pathwaycomprises a second via hole extending through the second ceramicsubstrate, a second ceramic/platinum mixture disposed in the second viahole in a sealed relationship with the second ceramic substrate, and asecond substantially pure platinum body disposed in a sealedrelationship extending through the second ceramic/platinum mixtureopposite the second ceramic substrate.
 25. The electrochemical cell ofclaim 22, wherein the precious metal disc hermetically sealing the firstsubstrate annular wall to the second ceramic substrate is selected fromthe group of gold, platinum, and palladium.
 26. The electrochemical cellof claim 22, wherein the first, second and third sinteredceramic/platinum mixtures individually comprise, by weight %, from 10:90ceramic:platinum to 90:10 ceramic:platinum.
 27. The electrochemical cellof claim 22, wherein the first, second and third sinteredceramic/platinum mixtures individually comprise, by weight %, from 70:30ceramic:platinum to 30:70 ceramic:platinum.
 28. The electrochemical cellof claim 27, wherein the first and second ceramic substrates areindividually selected from alumina and 3% YSZ.
 29. The electrochemicalcell of claim 22, wherein the electrode assembly is of either a primaryor a secondary chemistry.
 30. The electrochemical cell of claim 1,wherein the anode and cathode current collectors are individuallyselected from copper and titanium.
 31. The electrochemical cell of claim1, wherein the anode and cathode current collectors individually have athickness ranging from about 0.1 microns to about 50 micros.
 32. Theelectrochemical cell of claim 1, wherein the separator is comprised ofalumina.
 33. The electrochemical cell of claim 13, wherein the anode andcathode current collectors are individually selected from copper andtitanium and have a thickness ranging from about 0.1 microns to about 50micros.
 34. The electrochemical cell of claim 13, wherein the separatoris comprised of alumina.
 35. The electrochemical cell of claim 22,wherein the anode and cathode current collectors are individuallyselected from copper and titanium and have a thickness ranging fromabout 0.1 microns to about 50 micros.
 36. The electrochemical cell ofclaim 22, wherein the separator is comprised of alumina.